Mobile communications are increasingly provided by packet-based communication systems rather than legacy circuit-switched systems. A communication infrastructure known as IMS (IP multimedia subsystem), for example, is often used within cellular communication systems for providing voice, video, and other types of communications.
For certain types of communications, media such as audio and video are transferred in real time between communication terminals. For a voice call, as an example, a voice terminal captures an analog audio signal, converts the analog audio signal to a digital data stream, compresses the digital data stream in a process referred to as coding or encoding, and transmits the compressed digital data stream to another voice terminal. The receiving voice terminal receives the compressed digital data stream, decompresses the digital data stream in a process referred to as decoding, and converts the decompressed data stream to an analog signal to drive an amplifier and/or loudspeaker.
The coding and decoding use an algorithm that compresses and decompresses a digital media stream in accordance with an agreed upon media coding standard, so that the compressed media stream is in a corresponding audio coding format. The algorithm and/or the computer code implementing the coding and encoding is referred to as a codec.
For a given media type such as audio, there may be many different codecs, each of which implements a corresponding audio coding standard. Different devices may support different codecs, and translation between data streams of different coding formats may at times be performed. Translation such as this, from one coding format to another coding format, is referred to as transcoding.